As spinach consumers continued reporting more E. coli sickness on Monday, government investigators expanded their hunt for the cause beyond processors to Salinas Valley farms where E. coli has been found previously. Government and other experts said water on the farms could be a likely culprit, though that has not been proved.

Several investigators late Monday were to begin fanning out to farms in the Salinas Valley, which is believed to be the source of at least eight E. coli outbreaks since 1995.

“There are many possibilities. The most likely source of contamination initially is on the farm somewhere,” said David Acheson of the Food and Drug Administration’s Center for Food Safety and Applied Nutrition. He said it might be related “to water practices” of growers but would not rule out the possibility of processor problems, including inadequate chlorination and washing.

On a day when the number of cases grew from 102 to 114, federal and state officials stressed there is no smoking gun and have ruled almost nothing out. They are almost certain, however, that the contamination was not done deliberately.

Twice in the past two years, federal health officials told California growers of lettuce and other leafy greens, mostly in Salinas Valley, to make their farming practices safer. In a stern warning letter in November, an FDA official wrote “Foodborne illness investigations rarely pinpoint the point of origin of the contamination. However, claims that `we cannot take action until we know the cause’ are unacceptable.”

Water was a prime suspect then, specifically floodwaters from nearby creeks and rivers. The letter said that although it was unlikely that contamination in all of the outbreaks was caused by flooding from agricultural water sources, farmers should dispose of any ready-to-eat produce that comes in contact with floodwaters because the produce could be exposed to “sewage, animal waste, heavy metals, pathogenic microorganisms or other contaminants.”

After spending the past few days collecting records from Natural Selection Foods and River Ranch Fresh Foods, a company that bought spinach from Natural Selection Foods, and checking Natural Selection Foods’ San Juan Bautista processing plant, investigators are now also looking at several Salinas Valley farms that grow spinach for the processors. They plan to have the farmers walk through every step of their growing and irrigation techniques.

In addition to a dozen new cases, a second death, in Ohio, was being investigated Monday for links to the bad spinach. The Oakland daughter of a Wisconsin woman who died after eating contaminated spinach said she was still too distraught to talk about her mother’s death.

Midwestern states

On Monday, two more states, Illinois and Nebraska, also reported cases, bringing the total to 21 states. And for the first time, federal officials described who was getting sick: 75 percent are women, and 59 percent between the ages of 20 and 64. Sixty have required hospitalization, and 18 have contracted a type of kidney failure called hemolytic uremic syndrome, caused when red blood cells are destroyed. It can lead to permanent kidney damage and, sometimes, death.

The number of cases is likely to grow for at least another two weeks, given the incubation period of the illness, which can take up to a week to sicken individuals, and the lag between illness and reports to authorities, FDA officials said.

While investigators warned against reaching premature conclusions, experts said from everything they knew of the current outbreak, most signs pointed to E. coli-contaminated water. But proving it may be very difficult.

“If they use well water, it’s difficult to say where it came from,” said University of California-Davis scientist Dean Cliver, who suspects that irrigation water, perhaps drawn from a contaminated well, is the problem. The well water may have only been briefly contaminated.

“And it’s not like a stream, where you could see the source of contamination on the surface,” he said. “With well water, the technology to trace microbes is a lot more expensive.”

Cliver predicted that inspectors will test water and soil throughout the Salinas Valley farming region. “And if the past is any guide, they won’t find a thing,” he said.

Government investigators admit they have been stumped many times before.

California’s Public Health Officer Mark Horton said, “The smoking gun has not been identified at this point in time,” in either the current outbreak or the others traced to the Salinas Valley.

All told, about three dozen brands of bagged spinach and mixed salad have been recalled. The FDA does not have legal authority to demand a recall, and state officials, which can force removal of foods from the market deemed dangerous, have decided not to.

The FDA said it appears all of the spinach implicated in the outbreak was grown in California fields, but they still recommended that consumers avoid all fresh spinach products, pre-packaged or in a loose bundle. Most spinach this time of year is grown in California. State officials said DNA fingerprinting has allowed them to conclude the bacteria is all related to the same outbreak, but they refused to narrow down the possible causes.

But hearing of the reports of possible water contamination, Kevin Reilly, deputy director of prevention services for the state Department of Health Services, said Monterey County residents can safely drink their tap water, because drinking water systems are rigorously tested.

E. coli is often traced to fecal matter.

“The E. coli 0157 is certainly found in cattle but is found in other mammals as well,” including wildlife and human fecal matter. “At this point we just don’t know. All are possibilities.”

Long-lived microbe

Experts have long felt irrigation water may be the source of the repeated outbreaks.

“Contaminated irrigation water is one of the most common vehicles by which E. coli may be introduced into the environment,” concluded Abasiofiok Ibekwe of University of California-Riverside in his 2005 paper in the journal Environmental Science and Technology. He found that the microbe can persist for more than 45 days in soil.

Well contamination in Salinas Valley and elsewhere has been blamed for at least two other major outbreaks of disease due to produce contamination. In one of these cases, the well had not been shielded at the surface. The cause of bad well water was not identified in the second case.

In a third major outbreak, investigators found that lettuce fields had been flooded by water contaminated by cattle grazing in an adjacent field.

Underscoring the sensitivity of the investigations, Natural Selection Foods announced that early investigations have not found E. coli contamination in its organic spinach at this time. But the FDA quickly warned that it has not reached a final conclusion and said the investigation into both traditional and organic farming practices is ongoing.

Natural Selection Foods had said that because federal and state officials found manufacturing codes from spinach related to illnesses that didn’t match those of the company’s organic salads, those products were no longer suspected, but they are continuing the recall.

Lisa M. Krieger is a science writer for the Bay Area News Group, covering research, scientific policy and environmental news from Stanford University, the University of California, NASA-Ames, U.S. Geological Survey and other Bay Area-based research facilities. Lisa also contributes to the Videography team. She graduated from Duke University with a degree in biology. Outside of work, she enjoys photography, backpacking, swimming and bird-watching.

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In addition to evacuating 10 neighboring homes, deputies restricted pedestrian and vehicle traffic in the area while the sheriff's office bomb squad "safely disposed" of the explosives, officials said.